For producing a resinous shaped article having a desired shape such as a porous material or a particle, various processes have been utilized. For example, Japanese Patent Application Laid-Open No. 2825/2001 (JP-2001-2825A) discloses a process for producing a porous material, comprising melt-kneading a pore-forming agent fusible at a molding temperature and a high molecular substance such as a resin, molding the kneaded matter to make a full (non-porous) shaped article containing the pore-forming agent, and then washing out the pore-forming agent from the full shaped article with a solvent. This document mentions pentaerythritol, L-erythritol and others as a pore-forming agent, and water or an organic solvent such as an alcohol compound as a solvent for eluting the pore-forming agent (auxiliary component). According to this process, a porous material having uniform fine pores can be produced.
However, in the case where a proportion of a pore-forming agent (erythritol having a low melting point or pentaerythritol having a high melting point) in a resin composition is increased, the resin composition is deteriorated in melt-kneading property and the size uniformity of the generated pores is decreased. More specifically, in kneading of the resin and erythritol, melting of erythritol having a low melting point induces decrease in viscosity of the resin composition and remarkable deterioration in melt-kneading property of the resin composition. Moreover, a resin composition containing pentaerythritol at a high proportion can be melt-kneaded, however, part of pentaerythritol remains as an unmelted matter and it is impossible to obtain a porous material having a uniform pore size.
Japanese Patent Application Laid-Open No. 176065/1998 (JP-10-176065A) discloses a process for obtaining a spherical fine particle of a thermoplastic resin (a), which comprises melt-kneading the thermoplastic resin (a) to be powdered with other one or more of thermoplastic resins (b) to give a resin composition comprising the resin (a) constituting the dispersed phase and the resin (b) constituting the continuous phase, and washing the resin composition with a solvent capable of dissolving the resin (a) and incapable of dissolving the resin (b).
In this process, however, it is necessary not only that the dispersed phase and the continuous phase are incompatible with each other, but also that an applicable combination of the resin constituting the continuous phase with the solvent is selected depending on the kind of the resin of the dispersed phase. Therefore, the combination of the resins should be limited to a specific one, and in addition, the combination of the resin with the solvent should be limited to a specific one. Further, in a step of cooling the dispersed composition, the resins incompatible with each other tend to form a large phase in the separation. Therefore, if the dispersed composition is not carefully solidified, the once produced dispersed phases will be gathered or aggregated again, and as a result, it is impossible to obtain a spherical fine particle having a given shape.
Furthermore, the resin constituting the continuous phase is finally recovered, or discarded in a dissolved state, because of being uninvolved in the resin fine particle as a product. However, recovery of the resin in the solution not only is very difficult but also is a caused factor of increase in the production cost of the resin particle. Moreover, in the case of discarding the resin solution directly as a waste fluid, there is concern about adverse effects on the environment.
Japanese Patent Application Laid-Open No. 13816/1985 (JP-60-13816A) proposes a process for producing a thermoplastic resin particle, which comprises melting a polyethylene glycol and a thermoplastic resin with stirring, then putting the molten mixture in water to solidify the both polymers, and then removing the polyethylene glycol from the resulting matter with water. Japanese Patent Application Laid-Open No. 9433/1986 (JP-61-9433A) discloses a process for producing a thermoplastic resin particle, which comprises melting a thermoplastic resin and a polyethylene oxide with stirring, then cooling the molten mixture, and removing the polyethylene oxide from the mixture with water. Japanese Patent Application Laid-Open No. 165457/1997 (JP-9-165457A) discloses a process for producing a resin fine particle, which comprises mixing a melt-formable and water-soluble polymer (such as a polyvinyl alcohol-series resin, a denatured starch, or a polyethylene oxide) and a thermoplastic resin to give a melt-shaped product, and then removing the water-soluble polymer from the shaped product with water.
Even in these processes, however, since it is necessary that a resin and a water-soluble polymer are incompatible with each other, a selectable combination of the resin is limited, and in addition, the particle size distribution of thus resulting resin particle is insufficient in uniformity. Further, these water-soluble polymers having small solubilities to water need a large amount of water for dissolution, and in addition, significantly deteriorate productivity of resin particles due to the slow velocity of dissolution. Furthermore, since such water-soluble polymers are often derived from unnatural products, a waste fluid containing such a water-soluble polymer dissolved therein adversely affects on the environment.
It is therefore an object of the present invention to provide a water-soluble auxiliary component (or a water-soluble auxiliary agent) being a saccharide yet kneadable with a resin component uniformly, and a dispersed composition (or a resin composition forming a disperse system) obtained by using the water-soluble auxiliary component.
It is another object of the present invention to provide a water-soluble auxiliary component (or a water-soluble auxiliary agent) capable of forming a given shaped article industrially with advantage even in the case of using a wide range of a resin component, and a dispersed composition (or a resin composition forming a disperse system) obtained by using the water-soluble auxiliary component.
It is still another object of the present invention to provide a water-soluble auxiliary component (or a water-soluble auxiliary agent) capable of being kneaded even if contained in a high proportion relative to a resin component and capable of forming a uniform phase-separation structure with the resin component, and a dispersed composition (or a resin composition for forming a disperse system) obtained by using the water-soluble auxiliary component.
It is a further object of the present invention to provide a process for producing a shaped article by using a dispersed composition (or a resin composition forming a disperse system) comprising a water-soluble auxiliary component (or a water-soluble auxiliary agent) and a resin component, wherein the water-soluble auxiliary component can not only be easily eluted with water but also reduce the burden on the environment.
It is a still further object of the present invention to provide a process for producing a shaped article having a uniform pore size or a uniform particle size.